The invention relates to the field of installations and automatic processes for plasma-jet marking and for cutting or welding workpieces, in particular made of metals or plastics, such as plates or sheets of steel.
Automatic machines or installations For plasma-jet cutting have been used for many years to plasma-jet trim or cut geometrical or other shapes in metal workpieces, such as plates or sheets, in particular made of ferrous and non-ferrous materials.
Plasma cutting is based on the combined thermal and kinetic effects of a plasma jet, that is to say an electric arc created in a strongly constricted ionized-gas medium established between, on the one hand, an emissive element of the plasma torch, forming the cathode, and on the other hand, the sheet or workpiece to be trimmed, forming the anode, these two electrodes, known as the cathode and the anode, being respectively connected to the negative and positive terminals of a DC electricity source, such as a current generator.
Processes and installations for plasma cutting are described, for example, in documents EP-A-0040925, JP-A-02108464, U.S. Pat. No. 5,760,363 and EP-A-0599709.
In view of the progress made both as regards the characteristics of the plasma jets employed (composition of the plasma gas, structure of the electrodes of the plasma torch, power and shape of the plasma jet, etc.) and as regards the cutting machines themselves (numerical control, off-line programming centres, shaft actuators, mechanical structure for guiding and driving the shafts, etc.), it is now possible to integrate this type of plasma-cutting installation in an overall manufacturing line or process, with a view to improving productivity and/or production efficiency.
However, the machines or installations for automatic plasma-jet cutting which currently exist are for the most part usable only for trimming materials. In other words, the plasma jet delivered by a plasma torch with which a cutting installation is equipped will produce melting through the full thickness of the metal workpiece to be machined, so as to obtain trimming of this workpiece with a predefined geometry.
In a manufacturing process, however, at least three types of additions to the trimming operation often prove necessary, namely drawing geometrical markers on the workpieces, identifying the cut workpieces using a number or standardized code, and marking with a standardized code to provide traceability or tracking of the manufactured workpieces.
In general, these additional operations follow the operation of plasma cutting the workpiece, but it is not inconceivable that they may be, or may have also to be carried out before the said plasma-cutting operation in certain cases.
More precisely, the operation of drawing geometrical markers on workpieces which have been trimmed or are to be trimmed, may consist in drawing or marking, in particular:
either continuous or discontinuous positioning lines on workpieces or elements which are intended to be welded or assembled later; PA1 or centre points or centre-locating axes to facilitate subsequent operations of mechanically drilling holes of predefined diameter and position on the workpieces; PA1 or lines or markers for the positioning of tools for subsequently shaping the trimmed workpieces, for example tools for folding the said workpieces. PA1 at least one carrying structure, that is to say a support frame, carrying at least one plasma-marking torch and at least one cutting and/or welding torch, PA1 drive means capable of moving, preferably simultaneously or in a synchronized manner, at least the said plasma-marking torch and at least the said cutting and/or welding torch in at least one direction of motion; preferably in several directions or axes of motion, in particular along at least three orthogonal axes (X, Y, Z), PA1 coolant supply means capable of supplying at least the said plasma-marking torch and at least the said cutting and/or welding torch with at least one coolant, such as demineralized water, PA1 gas supply means capable of supplying at least the said plasma-marking torch and at least the said cutting and/or welding torch with at least one gas; the term gas is intended to mean either a single gas compound or a mixture of several gas compounds, PA1 electric-current supply means capable of supplying at least the said plasma-marking torch and at least the said cutting and/or welding torch with electric current, and PA1 control means capable of initiating at least one movement of the said plasma-marking torch and of the said cutting and/or welding torch relative to the said at least one workpiece to be marked and cut and/or welded. PA1 the control means are capable of controlling the said drive means so as to make it possible to move, preferably in a synchronized manner or simultaneously, at least the said plasma-marking torch along at least one path defining at least one part of the mark to be made on the said workpiece and/or at least the said cutting and/or welding torch along at least one cutting path and/or at least one path corresponding to a welding plane of the said at least one workpiece, PA1 the control means are capable of furthermore initiating at least one start and/or stop of the coolant, electric-current and/or gas supply to at least the said plasma-marking torch, and/or at least one start and/or stop of the coolant, electric-current and/or gas supply to at least the said cutting and/or welding torch, PA1 the control means are capable of controlling the said drive means in order to move the said plasma-marking torch and/or the said cutting and/or welding torch in several directions of motion, in particular in translation and/or rotation, PA1 the said drive means are motorized, the said drive means preferably comprising at least one electric motor and, optionally, at least one position encoder and/or at least one tacho generator, PA1 it furthermore has sensing means capable of allowing at least one determination of at least one parameter representing the distance separating the plasma-marking torch and/or the cutting and/or welding torch from a workpiece to be marked and/or cut and/or welded, and preferably, adjusting the said distance as a function of a parameter representing a desired distance value, PA1 it furthermore has workpiece-support means for carrying and/or holding, at least temporarily, at least one workpiece to be marked and/or cut and/or welded, PA1 it furthermore has means for delivering at least one workpiece to be marked and/or means for removing at least one marked workpiece, PA1 at least one cutting and/or welding torch and at least one plasma-marking torch are carried by the same moving subunit of the said carrying structure, PA1 the plasma-marking torch and/or the cutting and/or welding torch are selected from single- or double-flow plasma torches, PA1 the cutting and/or welding torch is selected from laser-welding or cutting torches and oxycutting torches, PA1 it furthermore has fume-extraction means and/or waste disposal means. PA1 the control means comprise numerical-control means, PA1 the plasma-marking torch and/or the cutting and/or welding torch are mounted on means with rails for moving the said marking torch and/or cutting and/or welding torch towards and/or away from the upper surface of at least one workpiece to be processed. PA1 (a) supplying at least one plasma-marking torch with at least one electric current and with at least one plasma gas, and generating at least one plasma-marking jet having a marking energy greater than or equal to a first energy threshold and less than a second energy threshold, the said first energy threshold corresponding to the minimum energy required to obtain at least one local change in coloration of the workpiece to be marked, and the said second energy threshold corresponding to the energy required to obtain complete melting through the full thickness of the said workpiece to be marked, PA1 (b) supplying at least one plasma-cutting torch with at least one electric current and at least one plasma gas, and generating at least one plasma-cutting jet having a cutting energy greater than or equal to the said second energy threshold corresponding to the energy required to obtain complete melting through the full thickness of the said workpiece to be cut, PA1 (c) plasma-jet marking the said workpiece to be marked by subjecting at least one part of the said workpiece to at least the said plasma-marking jet having the said marking energy, and PA1 (d) plasma-jet cutting the said workpiece to be cut by subjecting at least one part of the said workpiece to at least the said plasma-cutting jet having the said cutting energy. PA1 (a) supplying at least one plasma-marking torch with at least one electric current and with at least one plasma gas, and generating at least one plasma-marking jet having a marking energy greater than or equal to a first energy threshold and less than a second energy threshold, the said first energy threshold corresponding to the minimum energy required to obtain at least one change in coloration of the workpiece to be marked, and the said second energy threshold corresponding to the energy required to obtain complete melting through the full thickness of the said workpiece to be marked, PA1 (b) supplying at least one welding torch with at least one electric current and at least partially melting through the thickness of the said at least one workpiece to be welded, PA1 (c) plasma-jet marking the said workpiece to be marked by subjecting at least one part of the said workpiece to at least the said plasma-marking jet having the said marking energy. PA1 the plasma marking of the said workpiece to be marked is carried out along a predetermined marking path defining the marking to be made, PA1 the plasma-jet marking of the said workpiece is carried out prior to the plasma-jet cutting of the said workpiece.
Furthermore, the identification of workpieces which have been cut or are to be cut by a number or standardized code is also used to label various workpieces in order to identify them more easily and avoid any confusion between these various workpieces during subsequent operations. In fact, identification has, in particular, the advantage that it makes it possible to carry out relatively complex automatic programmes for plasma-jet trimming metal workpieces of highly varied geometries within a standard sheet-metal format, by fitting the said workpieces to be cut around one another in order to minimize loss or waste of metal and therefore optimize production costs.
Furthermore, marking workpieces with a standardized code guarantees that these workpieces are traceable, which is almost essential for companies receiving certification, such as a standard, confirming the quality of their manufacturing, who must be able to monitor the manufactured products that need to comply with this certification.
There are currently several marking systems which are or can be used according to their individual characteristics, the nature of the work to be carried out and the nature of the material or of the workpiece to be identified, namely, on the one hand, so-called "cold" markers, such as ink-jet marking, felt-pen labelling or using a pneumatic punch or electric graver, and, on the other hand, so-called "hot" markers, such as flame-heating the workpiece to be marked while spraying a marking powder, for example zinc powder, or marking the workpiece using a laser beam.
However, depending on the case, these various marking processes present drawbacks having relatively negative repercussions in industrial terms.
Thus, marking a workpiece with an ink jet or felt-pen is not ideal because this marking technique cannot be applied to certain materials, in particular to materials on which the ink pigments adhere poorly or not at all.
It has also been found in practice that this type of marking may, in certain cases, rub off fairly rapidly over the course of time, and that the workpieces then no longer have any identification marking, which poses problems of differentiating between these various workpieces in the subsequent steps of the production or machining process.
Similarly, marking using a pneumatic punch or electric graver may cause problems by deforming the workpiece, and these become all the more serious as the workpiece becomes thinner.
Furthermore, the technique of marking by spraying metal powder cannot be applied to all materials, given that, in particular, the problem arises of the marking powder's compatibility with the material of which the workpiece to be marked is made.
In addition, these marking techniques are often limited to a given material or family of materials, for example steels, and cannot in general be applied to workpieces made of very different types of material, for example metal workpieces and workpieces made of polymers or plastics.
On the other hand, document EP-A-865857 describes a process for marking sheet metal coated with paint, in which marks are made on the sheet metal by burning the paint locally with a plasma jet sheathed in a jet of cooling water. It will, however, be understood that this process is limited to marking coated sheet metal and cannot be applied to all types of sheet metal, that is to say irrespective of whether they are coated. Furthermore, according to this process, the upper surface of the sheet metal is not affected by the plasma jet, that is to say neither discoloured nor partially melted through its thickness, given that only the paint coating is burnt.
Other documents also propose processes for marking sheet metal. In this regard, mention may be made of documents U.S. Pat. No. 5,773,788, JP-A-62238020 or U.S. Pat. No. 5,760,363.
Document U.S. Pat. No. 5,760,363 proposes a plasma torch which can either cut or mark metal workpieces according to requirements.
However, several problems have not yet been resolved to date.
There is thus an industrial need to increase the productivity of marking and cutting or welding operations. This is because, at present, when it is necessary to carry out both cutting and marking, for example, on a workpiece such as sheet metal, the cutting is generally carried out first using a cutting torch located on a first support frame, then the plasma marking is carried out next using a marking torch located on a second support frame, and it is therefore essential to transfer the cut workpiece from the first support frame to the second support frame.
It is easy to see that, on the one hand, this entails significant encumbrance owing to the use of two support frames, as well as an installation for transferring workpieces from one frame to the other.
Furthermore, this type of installation requires each of the support frames to have its own means of moving the marking and cutting torches, of controlling the marking and cutting paths, and of positioning the torches, etc., and it will be easily understood that this, on the one hand, increases the complexity of the installation and, on the other hand, significantly increases its cost.
What is more, in this case, the operation of the two torches needs to be generated by different programmes independent of one another.
Put another way, with this type of installation, the problem arises of automating the marking and sequencing it in the overall manufacturing process, in particular sequencing it in relation to the prior or subsequent cutting and/or welding of the workpieces. This means that the machine or installation for marking the workpieces needs to be integrated in the production line, upstream or downstream of the cutting and/or welding installation; and to be managed, preferably, by the means for controlling and/or operating the overall installation, so as to make it start and stop at the appropriate time; to be secured, as regards the marking head proper, with the structure supporting the plasma-trimming torch in order to make it possible, preferably, to use the same drive shafts as those of the trimming and/or welding torch(es), and thus benefit from one-off management of the axes by the drive control means, such as a numerical control system, so as to obtain the same positioning accuracy.